Baalbek, Lebanon - Hezbollah has significantly increased its presence along Lebanon's northern border to prevent Syria's conflict from spilling into its territory, after recent Syrian Army gains ousted rebels in the region.

Sources within Hezbollah and close to Lebanon's Shia political-military group said more forces have been deployed to the border to prevent rebels fighting President Bashar al-Assad's army from entering the country. The mobilisation is also intended to thwart a repeat of last week's events when a barrage of rockets fired by Syrian rebels hit the historic town of Baalbek and surrounding areas.

Anyone we don't know, or think is suspicious, we stop and search them, and then hand [them] over to Hezbollah who will conduct investigations.

Ahmad, Baalbek villager

The rocket attack last Wednesday came hours after Assad's forces re-captured the strategic city of Qusayr after days of heavy fighting. Syrian rebels accused Hezbollah of sending thousands of fighters to join the battle on the side of Assad.

"We have increased the number of people on the border and the number of patrols conducted along there, and within the Lebanese territories to prevent armed groups from infiltrating," a Hezbollah member told Al Jazeera, on condition of anonymity for security reasons.

Other groups have set up armed patrols in key towns, such as Baalbek, conducting stop and searches of people deemed suspicious.

Baalbek, a town in the plains of the Bekaa Valley, is home to about 75,000 residents of a variety of religious sects. It is a popular tourist destination because of the ancient Roman ruins located in the town's centre.

"With Hezbollah concentrating on the border areas, we're running patrols in the towns and between the towns," Ahmad, a Baalbek resident and a member of the newly established patrols, told Al Jazeera.

"We all thought Hezbollah was protecting the whole area, but the rocket attacks showed there was a breach somewhere, so we took the initiative to help with security," said Ahmad, who gave only one name citing security concerns. "Now, anyone we don't know, or think is suspicious, we stop and search them, and then hand [them] over to Hezbollah who will conduct investigations."

Clan security

The Bekaa - known as the "tank of the resistance" because of the large number of fighters it has provided Hezbollah over the years - is also home to several of Lebanon's tribal clans, whose origins trace back to Arab tribes from centuries ago.

Clans are increasingly playing a security role in the area with numbers in the tens of thousands.

"We have a presence on the border because we are part of the defence system in the area," said Suleiman Chammas from the Chammas clan.

Already armed and using the training gained while serving in the Lebanese military, the clans are working in close coordination with Hezbollah, according to Chammas.

"We all have arms but the big operations are left to [Hezbollah] because they have the heavy weaponry," he said. "We just defend our towns and villages."

Originating in Syria, the Chammas clan has an estimated 45,000 members throughout Lebanon and also in parts of Syria. It is one of two original clans in the country, the other being the Hamadeh. Others include Nasreddine, Allaw, Dandash, Ala'eddine, which are offshoots from the two.

The clans typically mete out their own forms of justice, resolving issues through rulings by elders, rather than the local authorities. They have a reputation for being outlaws, and are said to be heavily involved in Lebanon's drug and smuggling trades.

Joining forces

Hashem Osman, a former mayor of Baalbek, sits in his home perched on a hill overlooking the sprawling town.

"Back in the day there used to be problems and scuffles between the clans and Hezbollah," Osman told Al Jazeera. "Today they are on the same path… A large majority of people from the clans are now part of Hezbollah, and have sacrificed their blood for the [Syrian] resistance."

According to Chammas, whose clan lost several members in the battle for Qusayr, the clans were neutral at the start of the Syrian conflict. But following a series of threats and cross-border kidnappings in the Bekaa by members of the Syrian opposition, the clans felt obliged to get involved.

"By attacking us in Lebanon [the Syrian rebels] are poking a hornets nest. What are they trying to achieve?" Chammas asked.

Osman echoed the sentiment, urging Syrian opposition fighters to think twice before launching any further attacks.

"Offending Baalbek is expensive and there is a high price to pay," he warned. "We ask them to keep their battle in Syria, or it will backfire heavily on them."

Hezbollah claims to be defending Lebanese residents in Syrian border areas, as well as protecting Shia shrines in Damascus. But its role in the Syrian conflict has polarised the Lebanese population, causing many to hold the group responsible for dragging the war into Lebanon.

Stoking further tensions, several towns and villages located on the northern border have become key military supply routes into Syria, whether for the rebels or for the regime.

But according to Osman, the rocket attacks have so far failed to divide or instill fear amid Baalbek's population.

"Their whole aim was to get people to stop supporting Hezbollah," he said. "This hasn't worked. People from Baalbek have martyrs returning from Syria, and they are offering more."

The civil war in Syria is also driving up tensions within religious sects.

Sami Ramadan is a Sunni high schoolteacher and resident of Iaat. The tiny village fell victim to the barrage of rockets last week, and Ramadan described how his brother's house was hit, wounding his 18-year-old niece.

"It's a miracle she survived. She bent down to pick something up from under the table, and the rocket hit. The table protected her," Ramadan said.

Such attacks show the "misguidance" of the Syrian rebels, he said. "I'm a Sunni and the house that was hit is a Sunni house… These attacks on us have a reaction from the Sunni street in the Bekaa, and it is against the Syrian armed opposition."

Ramadan said he feared a victory by the Syrian rebels. "I am an open-minded Sunni, and as far as the extremists fighting in Syria, I have 'strayed' so they'll come after me before they go after the Shias."

Divisions in Baalbek

Not everyone in Baalbek supports Hezbollah's role in Syria. Despite being an active member of the armed patrols and having lost family members fighting with Hezbollah in Syria, Ahmad made it clear he was not a supporter of the Shia militia's actions across the border.

There will definitely be more confrontations, and in a military aspect we are ready. Don't play with fire.

Suleiman Chammas, Baalbek villager

"Hezbollah took a decision, acting on behalf of us all, to fight in Syria," he said. "Well, I wasn't asked, and I don't support that decision. They don't need to be in Syria, they can defend Lebanon from the Lebanese territories, and just stay on the borders."

On Sunday in the capital Beirut, meanwhile, a protest against Hezbollah's involvement in the Syrian civil war turned violent with one demonstrator shot dead outside the Iranian Embassy.

But in Bekaa, most villagers support Hezbollah's mobilisation in Syria. That said, people here are more cautious about spending time outside for fear of further attacks by the rebels.

"The atmosphere has changed," Ahmad said. "Yes, there were huge celebrations after the battle of Qusayr, but I think these celebrations are premature… It is very likely we'll see more attacks."

Ahmad said about 20 percent of Baalbekis were opposed to Hezbollah siding with the Syrian Army. He said if the attacks continue, he would eventually leave the area.

Chammas, however, said his clan was preparing for the long haul. "There will definitely be more confrontations, and in a military aspect we are ready," he said, adding a warning to the Syrian rebels and their Lebanese backers: "Don't play with fire."